Regulation of motor-driven blowers



May 26, 1925. r 1,539,717

F. H. C. COPPUS REGULATION OF MOTOR DRIVEN BLOWERS Filed Nov. '2, 1921 Patented May 26, 1925.

UNITED STATES FRANS H. C. COPIPUS, OF WORCESTER, MASSACHUSETTS.

REGULATION OF MOTOR-DRIVEN BLOWERS.

Application filed November 7, 1921. Serial No. 513,497.

To all whom it may concern:

Be it known that I, FRANS H. C. CoPrUs, a citizen of the United States, residing at Worcester, in the county of Worcester and Commonwealth of Massachusetts, have invented a new and useful Improvement in a Regulation of Motor-Driven Blowers, of which the following, together withthe accompanying drawings, is a specification.

My invention relates generally to motor driven blowers, such as are employed for purposes of ventilating and drafting. The object of my invention is to provide an improved arrangement of the parts of a blower in connection with improved means for regulating the volume and pressure of the air delivered by the blower, whereby the amount,

of power consumed by the motor in driving the blower remains substantially constant at agiven speed of the motor, irrespective of the volume and pressure of the air delivered by the blower.

Motor driven blowers, as heretobefore constructed have not been notably successful. owing to the fact that the power consumed by the motor varies greatly with the volume and pressure of the air delivered by the blower, so that it is extremely diflicult to accurately determine the proper size of motor to employ for driving a blower which it is desired to operate at varying discharge pressures and rates of air delivery. When operating blowers of the centrifugal type, it is known that with a blower driven at a given speed, the power required to drive the blower varies directly with the effective area of the discharge opening, so that the blower motor must be able to develop enough power to drive the blower with the damper full open if necessary, without being overloa ed. This condition has resulted in the practice of providing motors which are able to develop much more power than that which would ordinarily be required to drive the blower with the discharge opening partiallyrestricted, as during normal operation of the blower.

When operating blowers of the propelled type, the conditions described above, with respect to centrifugal type'blowers, are reversed, for the propeller type blower consumes the least power when the blower inlet or outlet is fully open, and there is a minimum amount of resistance to the blower. Consequently, the power consumption of a propeller type blower increases rapidly as the inlet or outlet is restricted, and if, during the operation of a motor driven propeller blower, the inlet or outlet should become completely closed or the passage of air be otherwise obstructed, it is obvious that the power consumption of the motor would be so great as to cause it to be burned out. Here again, with blowers of the propeller type, themotor must be able to develop more than enough power to meet the extreme operating conditions.

From the foregoing, it is apparent that either centrifugal or propeller type blowers must be provided with much larger motors than the normal operating conditions require, which greatly increases the first costof the installation and, furthermore, results in inefficient operation of the motors when driving the blowers under ordinary load conditions.

By my invention I propose to provide an improved arrangement of the parts of a propeller type blower, whereby the power consumption of the motor will remain substantially the same at a given speed, irrespective of the volume and pressure of the air delivered by the blower, which maybe readily regulated by means of a damper or valve. These and other advantageous features of my invention will hereinafter more fully appear, reference being had to the accompanying drawings, in whiclr Fig.1 is a view, partially in section, and partially in side elevation, of a motor driven blower embodying my invention.

Fig. 2 is a view of the portion of the parts shown in Fig. 1, illustrating a modification in the operation of the damper for controlling the discharge of the blower.

Fig. 3 is a transverse sectional view along the line 33 of Fig. 1.

Like reference characters refer to like parts in the different figures.

Referring to Fig. 1, theblower generally consists of a frusto-conical casing 1, within which is adapted to rotate a plurality of 25 reasons which will hereinafter appear, irrecurved propeller blades 2 formed on a hub 3 which is mounted upon, and keyed to, a shaft 4. The shaft 4 is directly connected 'to the armature shaft of an electric motor shown in Fig. 3, the curvature of the guide vanes 7 is opposite to the curvature of the propeller blades 2, so that the edges of the vanes 7 are substantially at right angles to thevedges of the blades 2. Vith this arrangement of blades 2 and vanes 7, I have discovered that when the shaft 4 is driven at a given speed by the motor 5, the power consumed by the motor 5 in driving the blades 2 remains substantially constant for spective of the volume and pressure of the air delivered by the blower, which is adapted to be controlled by means of a regulating device which will now be described.

A plurality of shutters 9 are respectively mounted on shafts 10 at the open end of the motor casing 6. Each shutter 9 is provided with an arm 11, by means of which it may be turned on its pivot, and all of the arms 11 are connected by a link 12 through which all of the shutters 9 may be turned in unison. The pivot shaft 10 of one of the shutters 9 is extended, and has mounted thereon a worm wheel 13 which is in mesh with a worm 14. The worm 14 is journalled on the casing 6 and is adapted to be turned by means of a hand wheel 15. By turning the hand wheel 15, the shutters 9 may all be moved in unison to regulate the effective area of the inlet opening to the blower casing' 1. In thisway, the volume and pressure of the air delivered by the blower, with the ropeller blades 2 driven at a given speed y the motor 5, may be readily controlled and the blower will operate at various inlet openin 's with the consumption of a substantially constant amount of power by the motor 5.

While the above described meansof regulating the output of the blower by means of the shutters 10 is effective under ordinary operating conditions, yet it will be readily seen that it is ossible to so restrict the air inlet that hard y any air would be delivered by the blower, while the motor would con tinue to operate at substantially the same speed as before. VVhi-le such a condition of operation would not in any way endanger the motor 5, yet it would result in a useless the shutters 9 have been substantially closed,

I provide means whereby the motor 5 will be automatically disconnected from its source of power should the shutters 9 be closed beyond a predetermined point.

Referrlng' to Fig. 2, the shutters 16 are connected by a suitable link 17 in the same manner as the shutters 9 in Fig. 1, and one shutter is rovided with an arm 18, by means of wliich all of the shutters 16 may be moved in unison, A vertically movable rod 19 is provided at its lower end with a slot 20, within which is received a pin 21 connected to the arm 18. The upper end of the rod 19 is connected to a suitable damper regulator which may be of any desired form and is here shown, for the purpose of illustration, as a bell crank lever 22, which may be moved into any one of a number of different positions that are. indicated by notches- 23 to represent varying degrees of shutter opening. The rod 19 is provided with a pair of adjustable sto s 24 and 25, between whicha head 26 is adapted to move. The

head 26 is connected to a rocker shaft 27 by means of a link 28, and a weight arm 29 is.

mounted to turn with the. shaft' 27. A

switch arm 30 is also mounted on the shaft 27 and is adapted to make contact with a With the damper regulator lever 22 in'the' position shown, the shutters 16 are partly open; and the weight arm 29 is substantially in a vertical or balanced position. Should the lever '22 be moved to the right to open the shutters 16 further, the stop 24 will engage the head 26 and move it upward. whereupon the shaft 27 will be turned enough to cause the weight to fall to the right. This movement of the weight arm 29 causes the switch arm 30 to move to the left along the segment 31, so that the motor 5 will remain connected to the source of energy as long as the lever 22 occupies any the position shown in Fig. 2, to close the shutters-16 beyond a pre ermiued p'oiut,

the upper stop 25 will engage the head 26 and cause the weight arm to fall to the le ft, thereby causing the switch arm 30 to move off the segment 31 and disconnect the motor 5 from the source of energy. The motor 5 will remain disconnected so long as the shut ters' 16 are closed beyond the predetermined point, but the lower stop 24 will engage the head 26 and move the switch arm 30 into engagement with the segment 31 a ain as soon as the shutters 16 are opened enough to raise the weight arm 29 to a substantially vertical position. Obviously-,the exact degree of shutter opening at which the motor is connected or disconnected can be predetermined by properly positioning thestops 24 and 25 on the rod 19. Obviously also, the shutters 16 can be operated by a hand wheel, as in Fig. 1, and yet be associated with the weight arm 29 and switch arm 30 to auto matically connect and disconnect the motor 5, in accordance with the degree of shutter opening. 7

As previously stated, I have discovered that the power consumed by the motor 5 in driving the blades 2-remains substantially constant, irrespective of the volume and pressure of the air delivered by the blower,

and I attribute this result to the coaction' ters are opened. lVith the above described function of the vanes 7 in mind, it would therefore seem that as the shutters 9 are opened, the dynamic pressure represented by the velocity of the air leaving the blades 2 is transformed into static pressure by impact with the vanes 7, so that the power consumption of the motor remains constant as long as its speed remains the same. In

other words, the motor has substantially the same resistance tb overcome in driving the blades 2, irrespective of whether the vanes 9 are fully opened or fully closed.

From the foregoing, it is apparent-,that I have provided an improved arrangement of the parts of a propeller type blower whereby the power consumed by the motor which drives the blower remains substantially con stant, irrespective of the volume and pressure of the air delivered by the blower, and whereby these quantities may be readily "aried by my improved regulating device, which is adapted to automatically connect and disconnect the motor in accordance with the degree of shutter opening. While I have shown my invention as embodied in a particular arrangement of parts, it is not so limited but is susceptible of various modifications within the scope of the appended claims.

I claim, I

1. In a blower, the combination with a set of propeller blades driven at a predetermined speed and means for varying the volume and pressure of the blower discharge, of nieans for maintaining the power re uired. to drive the blower di erent rates of discharge.

2. In a blower, the combination with a set of propeller blades driven by a constant speed motor and means cooperating with said blades for maintaining the power consumption of said motor constant for varying rates of blower discharge, of means for regulating the volume and blower discharge.

3. In a'blower, the combination with a set ofpropelle'r blades driven by a constant speed motor and means cooperating with said constant. for

pressure of the blades for maintaining the power consumption of said motor constant for varying rates of blower discharge, of means-for automatically controlling the operation of said motor in accordance with the volume and pressure of the blower discharge.

4. In a'blower, the combination with a set of propeller blades driven by a constant speed motor and means cooperating with said, blades for maintaining the power consumption of said motor constant for varying degrees of blower discharge, of an adjust-able damper device for controlling the volume and pressure of the blower discharge.

5. In a blower, the combination with a setof propeller blades driven by a constant speed motor and means cooperating with said blades for maintaining the power consumption of said motor constant for varying rates of blower discharge, of'an adjustable damper device for controlling the volume and pressure of the blower discharge,

and means for controlling the operation of said motor in accordance with the setting of said damper.

6. In a blower, the combination with a set of propeller blades driven by a constant speed motor, means cooperating with said blades for maintaining the power consumption of said motorconstant for varying rates of blower discharge, and an adjustable damper device for controlling the volume and pressure of the blower discharge, of means for automatically controlling the operation of said motor in accordance with the settin of said damper.

7. In ailower, the combination with a set of propeller blades driven by a constant speed motor, means cooperating with said blades for maintaining the power consumption of said motor constant for varying rates of blower discharge, and an adjustable damper device for controlling the volume and pressure of the blower discharge, of means for automatically starting said motor when said damper device is opened a predetermined amount.

8. In a blower, the combination with a set of propeller blades driven by a constant s eed motor, means cooperating with said I) ades for maintaining the power consumption of .said motor constant for varying 10 rates of blower discharge, and an adjustable damper device for controlling the volume and pressure of the blower discharge, of means for automatically stopping said motor when said damper device is closed a 15 predetermined amount.

Dated this 25th day of October, 1921.

F. H. C. COPPUS. 

